THREESCALE-11281 - bump to go 1.21

[valerymo]

Jira: https://issues.redhat.com/browse/THREESCALE-11281

Verification

1. Install and sanity validation 3scale installed locally

cd 3scale-operator
make install
export NAMESPACE=3scale-test
oc new-project $NAMESPACE
oc project $NAMESPACE
make download
make run

Installed correctly routes/UI verified

~/go/3scale-operator oc project
Using project "3scale-test" on server "https://api.vmo01.xxxxx".
~/go/3scale-operator oc get deploy
NAME                 READY   UP-TO-DATE   AVAILABLE   AGE
apicast-production   1/1     1            1           43h
apicast-staging      1/1     1            1           43h
backend-cron         1/1     1            1           43h
backend-listener     1/1     1            1           43h
backend-redis        1/1     1            1           43h
backend-worker       1/1     1            1           43h
system-app           1/1     1            1           43h
system-memcache      1/1     1            1           43h
system-postgresql    1/1     1            1           43h
system-redis         1/1     1            1           43h
system-searchd       1/1     1            1           43h
system-sidekiq       1/1     1            1           43h
zync                 1/1     1            1           43h
zync-database        1/1     1            1           43h
zync-que             1/1     1            1           43h

2. CVEs analysys Quay.io Security Scan - Passed

• Image was built to see CVE check in Quay.io. Security Scan is running / will be updated
• Repo: quay.io/vmogilev_rhmi/3scale-operator:test-go121
• Command used to build image:

docker build . --platform linux/amd64 -t quay.io/vmogilev_rhmi/3scale-operator:test-go121